Novel hardware architecture for fast address lookups

For every packet an IP router receives, it makes a routing decision based on the packet's destination address. The router's forwarding rate is usually limited by the rate at which it can make these decisions. We describe a new method for implementing route lookups in hardware. Our method can be implemented in the forwarding engine of a network processor or router using a small on-chip SRAM and an off-chip DRAM, and it achieves a rate of one lookup per DRAM random access time. We present our method and discuss an implementation that uses a DRAM with 64 ns random access time to give over 15 million lookups per second. Our tests show that the method performs well for realistic routing tables while using only modest amounts of memory.